In some conventional reaction processes, for example, a culturing process of microbes, it is required that air or oxygen be supplied into a reaction liquid within a reaction vessel. In order to supply a required amount of air or oxygen into the reaction liquid, a method is widely used in which the air or oxygen is fed from the bottom of the vessel into the reaction liquid content by way of an appropriate air supply means, such as an air diffusion tube, so that the contact of the air or oxygen with the reaction liquid is actively performed. Further, the liquid content is usually stirred within the reaction vessel by employing an appropriate type of stirrer. However, in the case where a nitric component of the organic state is contained in the reaction liquid content or in the case of a biosynthesis of protein, such as culturing of microbes, the occurrence of liquid foam is extremely intensified. Thus, if it is desired to avoid applying any chemical defoamer to the reaction liquid, and if the conventional air supplying and stirring method is employed, the foam generated will necessarily occupy a great extent of the inner volume of the reaction vessel. As a result, the amount of the reaction liquid content to be charged into the reaction vessel must be kept small so as to prevent the generated foam from overflowing the reaction vessel. Further, in the case of culturing the microbes, the amount of microbes being displaced from the liquid content into the generated foam often becomes larger than that of the microbes remaining in the liquid content and as a result, the culturing efficiency must be kept low.
In some cases, a mechanical defoaming device having defoaming wings or a method of impacting foams by sound waves is used for collapsing foams appearing on the surface of a reaction liquid content in a reaction vessel. However, in both cases, additional complicated mechanisms or equipments including an electric power supply source for causing rotation of the defoaming wings, or a supply source of high-pressure gases for generating the sound waves are required. Therefore, there are many disadvantages from an economical perspective in view of the maintenance and life of the complicated mechanisms or equipments. Further, such defoaming device or impacting method often fails to eliminate the foam, if the occurrence of the foam is extremely turbulent.
Particularly in the case of the production of single cell proteins made from the raw materials of hydrocarbons such as normal paraffin or methane, the occurrence of the liquid foam is a serious problem to be solved. That is to say, in the case of hydrocarbon fermentation, a large amount of oxygen is required, and also the substrate must be emulsified in water, since the substrate is not soluble in water. Therefore, stirring of the emulsified culturing liquid must always be required. As a result, the amount of the occurrence of foam gradually increases during the middle of the culturing time period. As the culturing process approaches the final stage, the occurrence of foam on the surface of the reaction liquid rapidly increases. Thus, eliminating the foam which appears on the culturing medium liquid is indispensably required not only for attaining a normal culturing process but also for enhancing the culturing efficiency. However, no simple and effective method of eliminating foam has been acquired.